Films have been proposed, for example, in U.S. Pat. No. 3,887,745, having a biaxially oriented polypropylene layer and a uniaxially oriented polypropylene layer which is oriented only in the direction of film width. Such films have also been used as adhesive tapes employing the film as the support material. However, known films (or adhesive tapes) have disadvantages including inadequacy as to hand-cutting properties and drawing properties, and inability to provide clear and definite copies.
The present invention has, as an important object, preparation of an improved film and adhesive tape employing said improved film as a support material. More specifically, inadequacy as to hand-cutting properties causes appreciable inconvenience when the film is applied to stationery or home uses, since difficulties in hand-cutting imply difficulties in use. In the case of adhesive tape, tape dispensers provided with zigzag blades are employed in many cases, but ease of cutting with the dispenser is approximately proportional to that by hand. In other words, tapes which are readily cut by hand are also easy to cut with the dispenser. Laminated film composed of biaxially oriented and uniaxially oriented layers can be cut by hand with effort, but its cutting properties are not very good. Thus, such films are sometimes cut incorrectly even when the dispenser is used.
It has now been discovered that hand-cutting properties may be remarkably improved when a layer of propylene-ethylene block copolymer, (referred to as PEBC hereinafter) whether stretched uniaxially or biaxially, is laminated onto one surface of a laminate film composed of biaxially oriented and uniaxially oriented layers.
Moreover, since the PEBC layer exhibits excellent receptivity to writing or drawing when stretched, it is possible to draw or write on the resulting film. Indeed, adhesive tape having this film as the support material may be written upon clearly with either a pencil or a ball-point pen. Furthermore, if the PEBC layer is provided as a thin layer it transmits light with minimized irregular reflection. Thus, even when this film is stuck on or over a paper containing printed matter and the paper plus tape are subjected to copying, the film itself is not copied. Therefore a clear copy of the printed matter may be made without any reproduction of the adhered film. Suitability for copying as described above is one of the most important characteristics of the film, especially when adhesive tape having this film as the support material is used for mending breakage or tears in books, notebooks or the like.
By providing a thin PEBC layer on one surface of a laminate layer composed of the biaxially oriented and uniaxially oriented layers, its hand-cutting properties have been substantially improved, with simultaneous gain of highly desirable drawing properties and excellent suitability for copying. Moreover, adhesive tape having this film as the support material is extremely well suited to stationery uses and for general end uses at home.